Bonding

Metallic Bonding

Delocalised electrons are free to move and carry charge through the structure creating a current

Electrostatic forces hold the structure together

This means metallically bonded compounds have high boiling points

Uniform structure allows for malleability and ductility because ions slide past each other as they are the same size

Alloys affect properties because the ions are different sizes

Ionic Bonding

Between metals and non-metals

Metal donates electron to create a full outer orbital on the non-metal

Takes part in electrolysis

Creates a current when connected to a power source in an aqueous state

The opposite forces mean it has a high boiling point

It is a brittle compound because when bonds are moved they repel each other so compounds break up

Covalent Bonding

Electrons are shared as a pair

When one pair of electrons are shared this forms a sigma bond

Sometimes electron deficient molecules attach themselves to electron rich molecules forming a dative or coordinate covalent bond. This is when both electrons in the bond come from one molecule. When drawn an arrow is pointing towards the electron deficient molecule to show that both electrons have come from one molecule

Dative Bonding

Electronegativity

The ability of an element to attract electron density towards itself in a covalent bond

Electronegativity increases across a period and up the groupsHelium and noble gases are not electronegative as they don't form covalent bondsElectronegative elements are labelled as δ-

Electronegative elements:NitrogenOxygenFluorineChlorine

Shapes

A straight line means the bond is on the same planeA wedge means it is coming towards youA dashed line means it's going away

Need to know structure name and bond angle

Tetrahedral

Linear

Trigonal Planar

Octahedral

Trigonal Bipyramidal

Lone Pair Repulsion

The lone pair of electrons repel the other bonding pairs because they are closer to the central atom thus repelling the other bonds more.The general rule of thumb is each lone pair reduce the bond angle by 1.5º

V Shaped / Bent

Intermolecular Forces

- Van der Waal's Forces

This occurs because electrons in an atom are unlikely to be evenly spread - this is called a temporary dipole

When approaching another atom it will cause a temporary dipole in that atom because equal charges repel. This is aninduced dipole

These are weak forces

Temporary Dipole

Second atom has an induced dipole

Factors

The number of electrons

The mass/size of the atom

How close they can get together - branched molecules impede attraction and so have weaker VDW forces

This can be shown by looking at the standard states of group 7 elementsFluorine - GasChlorine - GasBromine - LiquidIodine - SolidThis shows that with the increase of electrons and size of atoms the boiling points increase because its harder to break the bonds of the larger elements

- Dipole-Dipole Forces

Occurs when there is a permanent dipole - when certain atoms are δ negative

This means the atoms are permanently electronegative

Electronegative elements are Nitrogen, Oxygen, Fluorine and Chlorine

Larger than VDW forces

Factors

Requires electronegative atoms to create a charge difference

- Hydrogen Bonding

When a free pair of electrons are attracted towards a δ positive Hydrogen

Only occurs between Hydrogen and either Nitrogen, Oxygen or Fluorine

Only occurs between covalently bonded molecules

Ices density is less than water's because the H bonds increase in length so to keep the water's bond angles the same.

Ice's structure. The Hydrogen bonds form a hexagonal structure

This means Hydrogen Bonded molecules always dissolve in waterHydrogen Bonds are also in DNA

Carbon Allotropes

Allotropes are different forms of carbon only structures

- Diamond

Carbon intetrahedron structure

Strong covalent bonds

This means it is a hard material

3700K melting point

Doesn't conduct electricity as no charged particles to carry charge

- Graphite

Trigonal Planar structure

Due to there being a pair not bonded this means there is a double bond but this double bond means it can be anywhere in the structure. This movement means graphite creates a current

Made of infinitely long layers of carbon. These are held together by VDW forces